1. Field of the Invention
This invention relates generally to electroerosive machining of metals, and more particularly to an apparatus for electroerosive piercing of holes in workpieces.
2. Description of the Related Art
There is known an apparatus for electroerosive piercing of holes in workpices (cf., PCT/SU 87/00099, filed Sept. 17, 1987). This prior art apparatus comprises an electrode holder with an electrode tool in the form of a rod placed with a clearance in a shell and projecting therefrom, and a means for moving, locking and wear-compensation of the electrode tool. This means includes parallel operatively interconnected driving and driven carriages each having a clamp for successively rigidly locking the rod of the electrode tool fashioned as movable and stationary jaws, the casing of each such carriage having through centering holes at the level of a clearance between the movable and stationary jaws, these holes being arranged coaxially with a passage provided in a pipe butt affixed to the lower part of the electrode holder. This passage receives, for axial displacements therein, the rod of the electrode tool the shell of which is rigidly secured to the pipe butt of the electrode holder coaxially with the rod, the electrode holder being fixedly attached to the driving carriage. The electrode holder can be hollow inside, and the interior of the electrode holder should preferably communicate with the passage receiving the rod of the electrode tool providing for the feed of a working fluid through the clearance between the shell and the rod of the electrode tool to the machining zone.
In the course of electroerosive machining, the driving carriage with the shell of the electrode tool secured thereon can move relative to the rod of the electrode tool mounted on the driven carriage in a direction opposite to the feed of the electrode tool to thereby compensate for part of the rod of the electrode tool being consumed during the electroerosive process.
However, this construction of the electroerosive apparatus including a feed drive, and driving and driven carriages carrying an electrode tool can find application only in stationary units, and therefore fails to pierce holes in large-size workpieces and in difficultly accessible locations.